中文摘要：

基于微扰量子色动力学（pQCD）的部分子模型，在领头阶（LO）近似下分别计算了质子-质子（P＋P）碰撞，Au＋Au和Cu＋Cu不同对心度碰撞产生π^0的强子谱和相应的核修正因子RAA．在考虑部分子喷注能量损失（即喷注淬火）效应后的理论计算表明，与相同质心系能量√s=200GeV的p＋P碰撞相比，Au＋Au或Cu＋Cu不同对心度碰撞产生的强子谱被压低，被压低的程度与依赖系统大小的能量损失有强烈的关系．系统越大，部分子喷注的能量损失越大，导致强子谱被压低得越多，RAA越小．理论计算的数值结果和实验数据相符合，说明能量损失机制的可靠性和真实性．

英文摘要：

Based on parton model in QCD, at the leading-order approximation we studied the π^0 spectra and nuclear modification factor RAA in Au＋Au and Cu＋Cu collisions with different centralities. Because of parton jet energy loss in heavy ion collision, large transverse momentum hadrons spectra are suppressed as compared to p＋p collisions at the same energy. It is shown that the suppression has strong dependence on the system size which determines the amount of the jet energy loss. The bigger the system is, the larger parton energy loss is. It results in the much more suppression of the spectra and also the much less RAA.